Choose the portfolio from the following set that is not on the efficient frontier.
a. expected return of 10 percent; stnadard deviation of 8 percent.
b. expected return of 18 percent; stnadard deviation of 13 percent.
c. expected return of 38 percent; stnadard deviation of 38 percent.
d. expected return of 15 percent; stnadard deviation of 14 percent.